Effects of Weed and Invertebrate Control on Alfalfa Establishment in Oat Stubble

Abstract

Crop residues in conservation tillage can provide excellent habitats for invertebrates that feed on alfalfa seedlings. The impact of invertebrate feeding on seedlings has been assessed for alfalfa no-till seeded into wheat (Triticum aestivum L.) stubble and grass sods, but not oat stubble. Thus, our objective was to determine the influence of weed and invertebrate control on alfalfa (Medicago sativa L.) establishment in oat (Avena sauva L.) stubble. Alfalfa was drilled into a plowed seedbed or into oat stubble. Postplant weed control (none or sethoxydim) and slug and insect control (plowing, methiocarb bait [3,5-dimethyl-4-(methylthio)phenol methylcarbamate], carbofuran [2,3-dihy-dro-2,2-dimethyl-7-benzofuranyl methylcarbamate], methiocarb plus carbofuran, and none) treatments were evaluated during the establishment of alfalfa at the Rock Springs Agricultural Research Center in Centre County, PA, on a silt loam (Typic Hapludalf; fine, mixed, mesic) soil. Slug numbers were measured 1,3, and 6 wk after planting. Seedling frequency and invertebrate feeding were measured 3 and 6 wk after planting. Morphological development was measured 6 wk after planting. Yields were taken the spring following planting. Reducing weed populations increased seedling shoot weight, trifoliolate leaves per plant, and production year first-cut yields. Invertebrate management decreased gray field slug (Derocerus reticulatum) populations and increased seedling frequency during initial seedling growth. Controlling volunteer oat was the major factor affecting establishment and yield of alfalfa no-till seeded into oat stubble.